Synthesis and characterization of toluene-3,4-dithiolatoantimony(III) derivatives with some oxygen and/or sulphur donor ligands

Article abstract of DOI:10.1016/j.saa.2009.05.006

Replacement reactions of toluene-3,4-dithiolatoantimony(III) chloride with oxygen and/or sulphur donor ligands like benzoic acid, thiobenzoic acid, thioacetic acid, phenol, thiophenol, sodium salicylate and thio glycolic acid in 1:1 molar ratio as well as

Full text of DOI:10.1016/j.saa.2009.05.006

Spectrochimica Acta Part A 74 (2009) 67–73
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis and characterization of toluene-3,4-dithiolatoantimony(III)
derivatives with some oxygen and/or sulphur donor ligands
H.P.S. Chauhan∗, Sumit Bhatiya, Abhilasha Bakshi
School of Chemical Sciences, Devi Ahilya University, Takshashila Campus, Khandwa Road, Indore 452001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Replacement reactions of toluene-3,4-dithiolatoantimony(III) chloride with oxygen and/or sulphur donor
ligands like benzoic acid, thiobenzoic acid, thioacetic acid, phenol, thiophenol, sodium salicylate and
thio glycolic acid in 1:1 molar ratio as well as disodium oxalate in 2:1 molar ratio in refluxing anhy-
drous benzene yielded toluene-3,4-dithiolatoantimony(III) mono oxo and/or thio carboxylic or phenolic
Received 3 February 2009
Received in revised form 16 April 2009
Accepted 11 May 2009
derivatives of the general formula
{R = OOCC6H5, SOCC6H5, SOCCH3, OC6H5, SC6H5,
Keywords:
Toluene-3,4-dithiolatoantimony(III)
compounds
1H NMR
13 C NMR
TGA
OOCC6H4(OH) and SCH2COOH} and
These newly synthesized derivatives are yellow and brown solids/liquids and are soluble in common
organic solvents like benzene, chloroform, dichloromethane, etc. These derivatives have been character-
ized by melting point determination, molecular weight determination, elemental analysis (C, H, S and
Sb), spectral {UV, IR and NMR (1H and 13 C)} and thermal (TGA, DTA and DSC) studies.
© 2009 Elsevier B.V. All rights reserved.
DTA
DSC
1. Introduction
dithiolatoantimony(III) oxo and/or thio carboxylic and phenolic
compounds of the general formula
R = OOCC6H5, SOCC6H5, SOCCH3, OC6H5, SC6H5, OOCC6H4(OH),
SCH2COOH and 1/2 OOC–COO].
[where
Carboxylic and phenolic ligands are versatile in nature and
exhibit various types of coordination patterns with transition as
well as main group metals. Antimony(III) and bismuth(III) com-
pounds are of special interest from the stand point of oncology
[1]. Antimony has quite wide spread use in pharmacology for the
treatment of syphilis, fever, melancholy, pneumonia, epilepsy and
inflammatory conditions [2]. Organic antimony salts are used med-
ically to treat some tropical disease [3], especially in the treatment
of all forms of leishmenasis [4]. It has been reported that the
organoantimony(V) carboxylates possess potent in vitro activity
against certain cancer cells [5]. Compounds of organoantimony
find extensive application in chemotherapy [6–8], antimicrobial [6],
antiparasitic [7] and antitumor [8,9] activities. A large number of
antimony compounds have also been tested as bactericides [10],
fungicides [11] and antifertility agents [12].
2. Experimental
2.1. Materials and methods
All the experimental manipulations were carried out under
moisture-free conditions. Solvents (benzene, dichloromethane,
diethyl ether, chloroform, etc.) were purified by standard meth-
ods [25]. Toluene-3,4-dithiol (Alfa Aesar) and ligands {benzoic acid,
thiobenzoic acid, thioacetic acid, phenol, thiophenol, sodium sali-
cylate, thio glycolic acid and disodium oxalate (all Fluka and Merck
Germany)} were used as received without further purification.
Toluene-3,4-dithiolatoantimony(III) chloride [26] was prepared by
the reaction of antimony chloride(III) and toluene-3,4-dithiol in
equimolar ratio (1:1) in anhydrous benzene.
The corresponding mixed ligand antimony(III) derivatives with
carboxylic and phenolic ligands do not appear to have received
attention of chemists. We have reported some dithiolato As(III),
Sb(III) and Bi(III) derivatives with sulphur ligands [13–24], in
view of the interesting results obtained in our laboratory, we
report herein synthesis and characterization of some toluene-3,4-
2.2. Analytical methods and physical measurements
Antimony was estimated iodometrically [27] and sulphur was
estimated gravimetrically as barium sulphate [27]. Melting points
were determined on a B 10 Tech India Melting Point Apparatus and
are uncorrected. Molecular weights were determined cryoscopi-
cally in benzene. Carbon and hydrogen were analyzed at a Perkin
Elmer 2400 CHN Elemental Analyzer at SAIF, Panjab University,
∗
Corresponding author. Tel.: +91 0731 2460208 (office)/2365948 (home);
fax: +91 0731 2365782.
E-mail address: hpsc@rediffmail.com (H.P.S. Chauhan).
1386-1425/$ – see front matter © 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2009.05.006

Table 1
Analytical and physicochemical data of toluene-3,4-dithiolatoantimony(III) with oxo and/or thio carboxylic and phenolic ligands.
S. no.
Compounds
Empirical formula,
yield (%)
M.P. (◦C)
Molecular weight
found (calc.)
Color and state
Analysis (%): found (calculated)
Sb
S
C
H
1
C14 H11 O2S2Sb, 92
108
353(397)
Pale yellow solid
30.15 (30.66)
16.02 (16.14)
42.14 (42.34)
2.58 (2.79)
2
3
4
C14 H11 O1S3Sb, 96
C9H9O1S3Sb, 93
C13 H11 O1S2Sb, 76
149
142
–
408(413)
350(351)
353(369)
Pale yellow solid
Dark yellow solid
Brown liquid
29.35 (29.47)
34.52 (34.67)
32.54 (32.98)
23.21 (23.28)
27.22 (27.39)
17.30 (17.37)
40.37 (40.69)
30.68 (30.78)
42.03 (42.3)
2.47 (2.68)
2.54 (2.58)
2.76 (3.00)
5
6
C13 H11 S3Sb, 96
112
122
353(385)
403(413)
Light yellow solid
Pale yellow solid
31.58 (31.61)
29.30 (29.47)
24.47 (24.97)
15.45 (15.52)
40.47 (40.53)
40.63 (40.70)
2.41 (2.87)
2.49 (2.68)
C14 H11 O3S2Sb, 96
7
8
C9H9O2S3Sb, 89
91
351(367)
Pale yellow solid
33.05 (33.16)
26.16 (26.20)
29.17 (29.44)
2.47 (2.47)
C16 H12 O4S4Sb2, 95
–
621(640)
Brown semi-solid
37.92 (38.04)
20.02 (20.03)
–
–

H.P.S. Chauhan et al. / Spectrochimica Acta Part A 74 (2009) 67–73
69
Scheme 1. Reactions of toluene-3,4-dithiolatoantimony(iii) chloride with oxygen and/or sulphur donor ligands in 1:1 and 2:1 molar ratio.
Chandigarh (India). The UV spectra were recorded in chloroform
solution at room temperature on a Shimadzu UV-1600 UV–vis spec-
trophotometer within the range 200–500 nm. Infrared spectra were
recorded in the region 4000–400 cm−1 using a Bruker Vertex model
70 spectrophotometer as KBr disc and in the region 600–50 cm−1
as nujol mull over CsI disks using a Magna-IR Spectrophotometer-
550 instrument. 1H and 13C NMR spectra were recorded in CDCl3
solutions on a FT NMR Spectrometer Advance-II (Bruker) model.
Chemical shift values 1H and 13C expressed in ı ppm relative to
TMS.
3. Results and discussion
3.1. Synthesis and characterization
Toluene-3,4-dithiolatoantimony(III) derivatives have been syn-
thesized by the reactions of toluene-3,4-dithiolatoantimony(III)
chloride with oxygen and sulphur donor ligands in 1:1 and 2:1
molar ratio in refluxing anhydrous benzene for ∼5 h (Scheme 1). All
these derivatives are yellow and brown solids/liquids and are solu-
ble in common organic solvents like benzene, chloroform, acetone,
dichloromethane, DMSO, DMF, etc. These compounds along with
their analytical and physicochemical data have been summarized
in the Table 1.
The TGA, DTA and DSC analysis were carried out in inert atmo-
sphere. For the TGA and DTA studies, a Mettler Toledo, model
TGA/SDTA 551e and for the DSC studies, a Mettler Toledo, model
DSC 822e, were used.
3.2. Electronic spectra
2.3. Preparation of toluene-3,4-dithiolatoantimony(III)
complexes with oxygen and sulphur donor ligands
The electronic absorption spectral data of these mixed toluene-
3,4-dithiolatoantimony(III) derivatives with oxygen and/or sulphur
donor ligands are listed in Table 2 and tentative assignments of
the important characteristic bands have been made with the help
of earlier publications [15–19,28]. The electronic spectra of these
newly synthesized antimony complexes exhibit three bands. In all
the antimony complexes, the ␲–␲* and n–␲* transition are due
to oxygen and/or sulphur ligand moieties and ␲–␲* intramolecu-
lar charge transfer transitions due to toluene moieties overlap and
exhibit most intense broad band in the range 200–280 nm. The sec-
ond band appears as a shoulder (220–285 nm) and is assigned to
␲–␲* transition in the C O (ligand) group. The third band of low
To the solution of toluene-3,4-dithiolatoantimony(III) chloride
(293 mg; 941 ␮mol) in benzene (∼25 ml) was added drop wise ben-
zene solution (∼25 ml) of benzoic acid (115 mg; 941 ␮mol). The
contents were heated under reflux for ∼5 h and liberation of HCl
gaswasobserved. Thesolventwasremovedunderreducedpressure
and a pale yellow solid product thus obtained was recrystallized in
CH2Cl2. Yield 340 mg; 92% M.P. 108 ◦C (Table 1).
All the other derivatives were prepared by adopting a similar
method; pertinent analytical and physicochemical data are listed
in Table 1
Table 2
Some relevant UVa and IR spectral data of toluene-3,4-dithiolatoantimony(III) complexes.
C. no.
I
II
III
ꢀ(C–H)
␯(C O)
ꢀ(C–O)/ꢀ(C–S)
ꢀ Asy.
ꢀ sy.
Sb–O
Tri substit. ring
Sb–S
1.
2.
3.
4.
5.
6.
7.
8.
250–260
235–265
200–220
260–280
260–275
260–277
–
265
275
230
220
250
285
–
310
315
310
305
315
325
–
3600(m)
3600(s)
3535(s)
3545(s)
3600(s)
3590(s)
3600(m)
3610(s)
1690(m)
1660(s)
1650(m)
–
1320(w)
922(w)
910(s)
1225(m)
925(s)
1325(m)
920(m)
1315(w)
1610(s)
1250(s)
510(m) 730(s)
320(w)
310(w)
315(w)
320(w)
320(w)
310(w)
315(w)
315(w)
–
–
–
–
–
–
–
–
–
725(s)
705(s)
520(m) 660(s)
695(s)
510(w) 660(s)
–
–
–
1665(m)
1680(s)
1685(s)
1600(s)
1580(s)
1590(s)
1240(w)
1350(w)
1360(w)
–
695(s)
710(s)
–
–
–
520(m)
s = sharp, m = medium and w = weak.
a
max/nm.

70
H.P.S. Chauhan et al. / Spectrochimica Acta Part A 74 (2009) 67–73
Table 3
1H and 13 C NMR spectral data (ı ppm) of toluene-3,4-dithiolatoantimony(III) complexes with oxo and/or thio carboxylic and phenolic ligands.
Com. no.
1
Compound
1H NMR chemical shift (ı ppm)
13 C NMR chemical shift (ı ppm)
2.34, s, 3H (ring CH3)
20.49 (ring CH3)
6.92, d, 1H {ring CH(6)}; j(ring protons) = 8 Hz
128.51 {C6H5–C(3 and 5)}
129.56 {C6H5–C(1)}
130.22 {C6H5–C(2 and 6)}
133.79 {C6H5–C(4)}
135.79 {ring C-2,5 and 6}
136.59 {ring C-1}
7.38, s, 1H {ring CH(2)}
7.51, m, 6H {ring CH(5) and C6H5}
140.01 {ring C-3 and 4}
171.24 {COO}
2
2.28, s, 3H (ring CH3)
20.45 (ring CH3)
6.92, d, 1H {ring CH(6)}; j(ring protons) = 8 Hz
125.67 {C6H5–C(3 and 5)}
128.03 {C6H5–C(1)}
128.46 {C6H5–C(2 and 6)}
129.05 {C6H5–C(4)}
129.41 {ring C-2,5 and 6}
130.12 {ring C-1}
7.47, m, 7H {ring CH(2, 5 and C6H5)}
134.49 {ring C-3 and 4}
3
4
1.73, s, 3H (CH3)
2.34, s, 3H (ring CH3)
16.23 (CH3)
20.50 (ring CH3)
135.80 {ring C-2,5 and 6}
136.65 {ring C-1}
140.03 {ring C-3 and 4}
6.92, d, 1H {ring CH(6)}; j(ring protons) = 8 Hz
7.38, s, 1H {ring CH(2)}
7.44, d, 1H {ring CH(5)}; j(ring protons) = 8 Hz
2.34, s, 3H (ring CH3)
20.48 (ring CH3)
7.11, m, 8H {ring protons and C6H5}
115.81 {C6H5–C(2 and 6)}
126.62 {C6H5–C(4)}
129.53 {C6H5–C(3 and 5)}
130.21 {ring C-2,5 and 6}
135.68 {ring C-1}
140.01 {ring C-3 and 4}
155.49 {C6H5–C(1)}
5
6
2.34, s, 3H (ring CH3)
7.35, m, 8H {ring protons and C6H5}
20.48 (ring CH3)
126.69 {C6H5–C(4)}
128.53 {C6H5–C(2,3,5 and 6)}
129.51 {C6H5–C(1)}
130.22 {ring C-2,5 and 6}
135.21 {ring C-1}
137.04 {ring C-3 and 4}
2.29, s, 3H (ring CH3)
20.40 (ring CH3)
6.94, d, 1H {ring CH(6)}; j(ring protons) = 8.4 Hz
7.32, m, 5H {ring protons CH(2) and C6H4}
7.85, d, 1H {ring CH(5)}; j(ring protons) = 8.4 Hz
10.38, s, 1H {OH}
117.10 {C6H4 (C3)}
118.83 {C6H4 (C4}
125.57 {C6H4 (C6)}
129.32 {C6H4 (C5)}
129.99 {C6H4 (C1)}
130.46 {ring C-2,5 and 6}
134.34 {ring C-1}
135.32 {ring C-3 and 4}
161.85 {C6H4 (C2–OH)}
172.61 {COO}
7
8
2.26, s, 3H (ring CH3)
3.64, s, 2H (SCH2)
20.49 {ring CH3}
42.66 {SCH2}
6.80, d, 1H {ring CH(6)}; j(ring protons) = 8 Hz
130.27 {ring C-2,5 and 6}
135.50 {ring C-1}
140.29 {ring C-3 and 4}
176.31 {COO}
7.29, s, 1H {ring CH(2)}
7.32, d, 1H {ring CH(5)}; j(ring protons) = 8 Hz
2.29, s, 6H (ring CH3)
6.72, m, 6H {ring CH(2, 5 and 6)}
20.47 {ring CH3}
130.21 {ring C-2,5 and 6}
135.69 {ring C-1}
140.06 {ring C-3 and 4}
176.83 {COO}
Note: s = singlet; d = doublet; m = multiplet.

H.P.S. Chauhan et al. / Spectrochimica Acta Part A 74 (2009) 67–73
71
Table 4
Thermal analyses (TGA, DTA and DSC) of toluene-3,4-dithiolatoantimony(III) thioacetate.
Step
TGA
DTA
DSC peaks
aTemp. range ◦
C
Total loss (%)
Different loss, %
found (calcd.)
Remaining fragments
Temp. (◦C)
Type of reaction
Temperature (◦C)
I
II
100–370 A
350–590 A
38.71
52.95
38.71 (39.07)
52.95 (51.63)
52.95 (51.63)
CH3–CH2–CH3 + (1/2)(Sb2S3)
(1/2)Sb2S3
Remaining material ((1/2)Sb2S3) A = 47.05 (48.37)
240
–
Endo.b
–
124 Exo.b, 132 Exo., 143 Endo.,
Total loss, % B = 52.95
a
A =
b
Endo.: endothermic process and Exo.: exothermic process.
intensity at 305–325 nm is attributed to n–␲* or charge transfer
transition due to ligand moiety.
appreciable shifts from the reported values [13,14,19,24,35]. In all
these derivatives a sharp singlet has been observed in the region
2.26–2.34 ı ppm due to ring methyl protons. These derivatives also
show a sharp singlet in the region 7.29–7.38 ı ppm due to ring
C2 proton and two doublets in the region 7.32–7.85 ı ppm and
6.80–6.94 ı ppm due to ring C5 and C6 proton respectively but in
the complexes containing phenyl protons in ligands exhibit signals
in the same region giving a multiplet in the region at 6.80–7.80 ı
ppm.
3.3. Infrared spectral data
The infrared spectra of all these newly synthesized compounds
have been recorded in the range 4000–200 cm−1 and tentative
assignments of the important characteristic bands (Table 2) have
been made with the help of earlier publications [29–34].
In addition, these compounds also show expected proton res-
onances due to corresponding carboxylic and phenolic proton of
ligands moieties (Table 3).
The bands of medium to strong intensity observed in the
region 1575–1700 cm−1 and 1250–1410 cm−1 may be attributed
to asymmetric carboxylate anion
and symmetric car-
3.5. 13C NMR spectral data
boxylate anion stretching vibrations of carboxylate
moieties, respectively. This asymmetric carboxylate anion stretch-
ing vibration is shifted in higher frequencies in all the carboxylate
derivatives. This shifting is indicating most probably monodentate
behaviour of carboxylate ligands with antimony.
The infrared spectrum of sulphur donor ligands [29] complexes
displaystwocharacteristicbandsat1685and922 cm−1 respectively
due to C O and C–S bond stretching vibrations. Bands present in
the region 310–320 cm−1 is due to (Sb–S) stretching vibration. In
addition, the bands appearing in the region 730–660 cm−1 may be
attributed to an asymmetrically trisubstituted benzene ring.
The 13C NMR spectra of these derivatives have been recorded
in CDCl3 solution using TMS as an internal standard. The 13C NMR
signals thus obtained are at reported values [13,19,24,35] without
any appreciable shifts.
The 13C NMR spectra of all these derivatives exhibit signal in the
region 20.40–20.50 ı ppm is observed due to ring methyl carbon
and in the range 134.4–140.24 ı ppm; 130.12–136.65 ı ppm and at
129.41–135.8 ı ppm due to ring carbon number C3, C4; C1 and C2,
C5, C6 resonances, respectively. In addition these derivatives also
exhibit the expected signals due to ligand moieties (Table 3).
3.4. 1H NMR spectral data
3.6. Thermal studies
The 1H NMR spectra of these derivatives have been recorded
in CDCl3 solution using TMS as an internal standard. The spec-
tra of these complexes exhibit the expected pattern without any
The mass losses, temperature ranges and final decomposition
products for toluene-3,4-dithiolatoantimony(III) thioacetate is pre-
Fig. 1. TGA of
.

72
H.P.S. Chauhan et al. / Spectrochimica Acta Part A 74 (2009) 67–73
Fig. 2. DTA of
.
Fig. 3. DSC of
.
sented in Table 4. The results show good agreement with the
theoretical formula as suggested from the analytical data. The com-
plex
showed double stage weight loss
(Fig. 1) in inert atmosphere.
This compound finally yields antimony(III) sulphide (Sb2S3) at
the end of the decomposition steps due to the decomposition of
organic part of the ligands. This compound may be attempted as
useful in a number of ways.
In the DTA curves (Fig. 2), decomposition of lig-
ands is represented as endothermic peaks at 240 ◦C
Fig. 4. Proposed structure of the complexes.
The DSC
(Fig. 3) exhib-
thus leading to a four coordinated distorted tetrahedral geometry,
with a stereochemically active lone pair of electrons (Fig. 4).
ited an exothermic change at 124 ◦C. Another exothermic change
observed at 132 ◦C followed by broad endothermic change at 143 ◦C,
exhibiting melting point of the complex.
Acknowledgements
3.7. Structural elucidation
Financial assistance from the University Grants Commission,
New Delhi is gratefully acknowledged. We are thankful to SAIF, Pan-
jab University, Chandigarh {for elemental analyses (C and H) and
spectral studies (for 1H and 13C NMR)}, UGC-DAE-CSR, Indore and
SAIF, IIT, Bombay (for FT-IR measurement) and CSMCRI, Bhavnagar
(for TGA and DTA studies).
Although it is quite difficult to comment on the molecular struc-
ture of these complexes in solid state without actual X-ray crystal
structure analysis at least one of the product. However on the basis
of the above spectral data it may be concluded tentatively that these
ligands behave as monodentate mode of attachment to the metal,

H.P.S. Chauhan et al. / Spectrochimica Acta Part A 74 (2009) 67–73
73
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